Architectural Designing of Modular Buildings and Modular Houses Part-II

Architectural Designing of Modular Buildings and Modular Houses Part-II

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modular building
Dr. A.N. Sarkar
Ex-Senior Professor (International Business) & Dean (Research), Asia-Pacific Institute of
Management, New Delhi

6.0. Construction Business with Innovative Cellular Structures, Modules and Buildings

Basically a cellular structure forms a fully functional part of building. A building can be constructed from cellular modules, which can be multiplied up to the full scale modular building. At the moment cellular structure technologies and their applications are well established and play a crucial role in particularly in aircraft manufacturing and marine industries. It is likely that large size cellular structures can have significant impact also on the building construction sector. Because the cellular structures are relatively new solutions in construction sectors, wide variety of research questions have to be addressed before the technology will have wider impact in the commercial markets. The research needs in the field of cellular structures are very wide covering structural design and analysis, building physics, architectural opportunities, life-cycle economics and building processes.

The term “modular” has many meanings, since forms and levels of modularity can have great diversity or variety (Starr, 2010). In the case of building construction the term modular has also several meanings. For example, a prefabricated element such as a window can be classified as a module (Sheffer, 2011). On the other hand, volumetric modules can be room size units (Lawson et al. 2011). Furthermore, modularity can have other types of appearances. Lennartson et al. (2009) have discussed not only about product modularity, but also process modularity and supply chain modularity, which both can have central roles in the production control of modular manufacturing. In this paper modular construction is understood to be a way where off-site construction is utilized widely in a way where dwelling sized modular units are produced.

Modular construction can be done either on-site or off-site. Bayd et al. (2012) have divided off-site construction into four categories: off-site pre-assembly, hybrid systems, panelized systems and modular buildings. In Europe the modular building industry has often resembled more an on-site construction production that has been moved into the interior conditions, than industrial manufacturing business (Linner & Bock, 2012).

In the Japanese modular construction industry, automation and new process innovations are reported to be widely utilized, whereas it has been claimed that in Europe the critical mass needed for the most efficient production processes is not usually achieved (Linner & Bock, 2012). According to Gann (1996) one key reason behind the success of Japanese industrialized housing might be in the ability to manage the whole supply chain in a way that takes into account the whole supply network, including manufacturing, sales and site erection. In proportion, one potential reason, why modular construction has not always been purely a success story, might be the challenges of supply chain management. Modular product architecture can require different kind of supply chain management solutions than on-site construction (Doran & Giannakis, 2011; Hofman et al., 2009).

Modular construction as a concept is not a new idea. The motivation behind this movement is in the promise to gain advantages related to standard procedures. Different approaches of modularity can be identified. Main possible approaches are: i) manufacturing of identical modules (no customization), ii) mass-customization of modules according to the needs of project in question, iii) manufacturing of free-form unique modules. Architectural possibilities are naturally increasing when going towards higher variability of modules. However, all approaches share the production philosophy where industrialized and standardized production is targeted.

Traditionally, buildings have been constructed using practices where on-site methods have had a dominating role. However, many kind of prefabricated solutions have gradually become more popular. This has resulted in prefabricated production technologies where complete building elements are formed from prefabricated components. For example, building façade elements can be composed from prefabricated components (skeleton, insulation, windows). Modularity can go even further. Modular construction refers to the use of volumetric modules that are objects in three physical dimensions forming a complete space such as room or even a completed dwelling.

A cellular structure is defined as a structural component targeting the minimization of the amount of used material to reach minimal weight and minimal material cost. A honeycomb shaped structure is an example of such cellular structure. Modular construction represents a new kind of skeletal structure (Hong et al., 2011). The basic idea is that the modules can bear the load of the other modules, and thus separate supporting structures are not required. Modular construction is also a special case of modular construction where even multi-storey buildings can be made from volumetric modules, the size of which can comprise a whole dwelling unit (Figure 1).

7.0. Automated Design of Modular Buildings

It may be argued that the construction starts at design phase of the built environment. The prime considerations of this phase is the advancement of automated design to improve cost-efficiency, enhance the lifecycle value of the project, and enable interoperability among a project’s lifecycle entities, and all these can result in significant cost savings. Accordingly, technology integration, with capabilities in 3-D design, analytical modeling and simulation and distributed intelligence, offers a great opportunity to create a truly integrated and automated design environment. It will greatly reduce errors through automated design optimization and verification. Optimization could include a variety of options including installation cost, lifecycle cost, and plant output. It should process design options in an accurate, scenario-based visualization environment.

The present day 3D modeling tools embed pre-defined objects that facilitate the development, routing, and connection of building systems in 3D, and provide conflict detection to identify physical interferences between components. 4D modeling tools (3D CAD model with time as its 4th dimension) link a construction project’s scope in 3D with its schedule to simulate the actual construction process. The benefits include the elimination of construction interferences, less reworks, fewer change orders, increased productivity and a decrease in delivery time, as detailed by Staub-French and Khanzod (2007). By reviewing project schedules in a 4D environment, and as referred in Yerrapathruni et al (2003), the construction professionals can readily identify design, constructability, sequencing and interdisciplinary interfacing issues.

7.1. Robotics Automation in Prefab Industry

Robots found its way to construction first in components making and the production of modular housing. Later, mobile robots were developed for special on-site construction tasks. As reported by Bock (2004), robots played active roles at the production line of Sekisui Chemical Sekisui Heim in Japan, where more than 85 percent of the houses are prefabricated. Bock (2007) elaborates a robotic precast concrete panel factory that uses a multipurpose unit which allows flexible production of the concrete floor, wall and roof panels. Here, according to certain CAD data, a multi functional gantry type robotic unit with two vertical arms places magnetos on the steel production table. The unit also attaches shutters on top of the magnetos and then places horizontal, vertical and triangular reinforcement bars, as per design. A CAD-CAM controlled concrete distributor spreads the right amount of concrete while controlled by a CAD layout plan, which takes into account installation, window or door openings.

Kye-Young Lee et al (2006) studied the human-robot cooperative (HRC) system to cope with the construction environment via real-time interaction with human and robot simultaneously. The power of a robot system helps a human to handle heavy materials with a scaled-down load. The human can feel and respond to the force reflected from the robot end-effecter acting with the working environment. The study also presents the experiments and evaluations to verify the HRC system for robotic applications giving the performance tests, like force assistance, force reflection, and position-tracking in a two axes manipulator. Westkamper et al (2000) developed a robotic system for the automatic laying of tiles within certain tolerances on prefabricated modules. The pilot work consisted of a tile laying system that consists of tile positioning equipment, a centering and measuring system and laying unit; an adhesive application system, consisting of adhesive preparation and transport unit; a tile supply system consisting of a store and a measuring unit; systems for generating process parameters; and handling and positioning systems having industrial robot and process control. Peñin et al (1998) and Paster et al (2001) developed a robotized cell for making the pre-fabricated glass reinforced cement panels for a Spanish construction company. It is developed for the automatic programming and control of facade panel manufacturing, and a CAD based 3D-drawing of the building facade serves as the input.

7.2. Modular Building in Automated Construction Site

An automated construction site may use robotics for logistics and assembly, but can face many barriers that are technological or economical. The technological barriers are that a robot must cope with the complexity of the construction process involving a dynamic and evolving site, together with the need for performing multiple tasks with differing characteristics. As detailed by Zied (2007), robotics research in construction has moved to address technological barriers via: a) development of mobile platforms and manipulators, b) development of control systems and sensory systems integration, c) re-engineering of processes to suit robotic systems, d) software development related to support the above, and use of advanced IT systems to enhance the whole system performance. Economical barriers also influence the implementation of a robotic system in construction, such as: a) the cost vs. benefits, b) the changes required for implementing the new system, and c) the effect of the new system on the complete organization, which includes health and safety, and labor unions concerns.

Martinez et al (2008) have reported on the robotization and industrialization of the construction process, with objectives on: a) Modular design of buildings, with robotic erection in construction; b) automatic planning and real-time re-planning of the offsite prefabrication, transportation, and onsite assembly; c) onsite automated transportation and assembly of prefabricated components. They also have developed tools for the assembly of various building components and modules. SMART (Shimizu Manufacturing system by Advanced Robotics Technology) represents a systems approach to computer-integrated construction. The system set-up takes a few weeks, after which the building’s top floor and roof are erected on top of four jacking towers. Jacking towers are used to push up the several-ton heavy top floor assembly -the main work platform – as well as lifting their own bases from floor to floor. The system is also composed of lifting mechanisms and automatic conveying equipment which are installed on the work platform. Overhead gantry cranes are connected to the underside of the roof structure. Trolley hoists are used to lift and position prefab components introduced at ground level, and floors emerge from under the top floor. The whole process is computer-controlled, though site workers oversee the operations.

 

 

7.2.1. Scheduling Automation and Sensor-based Control

An efficient production schedule drives automation in the actual creation of prefab components. Several scheduling prototypes have been reported, which addresses this issue. For example, a decision support system for coordinated prefabrication scheduling has been described by Chan and Zeng (2003). It supports key elements of production (re)scheduling, namely, conflict detection, determination of the priority for conflict resolution, generation and evaluation of alternatives for conflict resolution, and ranking of outcomes for negotiation. It combines the use of an explicit constraints-based scheduling model, and genetic algorithms (GA) to determine scheduling parameters and conflict resolution priorities. A GA based searching technique is also adopted in a mixed precast flow-shop scheduling system proposed by Leu and Hwang (2002), providing near-optimal combination of production sequences, resource utilization, and minimum make-span while complying with resource constraints and mixed production. Take notice that prior to construction, the components delivered to the site need to be inspected, stored and then tracked, while the details related to installation require adequate documentation. Prefab components locations need to be known, and transported to the site with minimum time loss. Gajamani and Varghese (2007) have presented a RFID-based location tracking real time scheduling and monitoring system that make use of prefab/ precast components. Data is collected in real time and is converted using a software system, not only for the control but also for field material management and future use.

7.3. Building Information Modeling (BIM) and Applications

The coordination and fabrication of the Mechanical, Electrical and Plumbing (MEP) systems in modular construction has always being one of the most challenging tasks encountered in the delivery process (Tatum and Korman, 2000; Korman, 2001; Lu, 2008). The MEP coordination and fabrication process involves defining the locations for components of building systems, in where are often congested spaces, to avoid interferences and to comply with diverse design and operations criteria. There are three primary reasons contributing to the challenges of MEP fabrication in modular construction. First, the process is highly fragmented between design and construction firms. Second, the level of technology used in different coordination scenarios has historically varied significantly between engineers and construction contractors. Third, historically the process did not provide a model for use by specialty contractors plan prefabrication (Korman, 2001). Using Building Information Modeling (BIM) to coordinate, document and fabricate MEP systems in modular constructions appears to be an effective approach to overcome these challenges (Figure 14).

BIM is commonly defined as the process of creating an intelligent and computable three-dimensional (3D) data set and sharing the data among the various types of professionals within the design and construction team. With BIM technology, an accurate virtual model of a building is constructed with precise geometry and relevant data needed to support the procurement, fabrication, on-site installation activities, as presented in Figure 15 (Eastman et al, 2008).

The use of BIM technology allows for the creation of intelligent contextual semantic digital models in terms of building elements and systems, such as spaces, walls, beams, columns and MEP systems, whereas 3D CAD technology is limited to generating drawings in graphical entities in terms of lines, arcs and circles. In addition, BIM technology allows for a creation of a model that contains information related to the building physical, functional and procurement information. For instance, the BIM model would contain data about the geometry, location, its supplier, operation and maintenance schedule, flow rates, and clearance requirements for an air-handling unit (CRC Construction Innovation, 2007).

Using BIM technology allows designers, engineers, and construction contractors to visualize the entire scope of a building project in three dimensions. Therefore, BIM technology is not only defined by simply creating a 3-D data set for internal analysis. When most professionals refer to a 3-D model today, they are only referring to a digital 3-D data set that contains geographical representations of objects placed in relation to each other. BIM technology is also known as the process of using a 3-D model and associated data set to improve collaboration among project participants. Using this collaborative approach, designers and builders can plan, in precise detail, the location and clearances required for a complete and successful project.

The implementation of BIM systems in modular construction normally involves in the following process:

Visualization: ability to create a 3D presentation of building modules geometry, location, space, contained systems in relation to each other

Modeling: ability to generate a 3D rendering tool to present the final product and finishes to owners, designers and constructors

Code reviews: allows for building officials and fire officials could use the 3D models with related data for code compliance reviews

Fabrication/ shop drawings: facilitates for the generation of detailed shop drawings could be easily produced once the BIM model is completed

Communication: facilitates simultaneously creation of construction documents, product imagery, rapid prototypes, exterior envelope, interior finishing, and MEP fixtures of building modules. Through this single information platform, BIM promote collaborations among the design team, consultant, constructors and the clients

Cost estimating: provides for cost estimating, material quantifications, and pricing to be automatically generated and modified while changes are applied for each building module

Construction sequences: provides a complete construction schedule for material ordering, fabrication, delivery and onsite installation of each building systems. With the integration of 3D rendering, 4 D (3D model + scheduling information) could be easily generated during the project design and construction phase

Conflict, interference and collision detection: ability to determine building system interferences which can be visually presented. For instance, an air distribution duct for the HVAC system physically interferes with a concrete beam.

Automated data exchange and wide usage of Building Information Model (BIM) play major roles in achieving construction automation. Technology wise, as noted in the Autodesk website. BIM is an approach to building design that is characterized by the creation and use of coordinated, internally consistent computable information about a construction project. The foundation of BIM is parametric building modeling, which records, presents, and manages not only object data at the component level, but also the network of relationships among all of the objects of the building from various views. From a lifecycle point of view, BIM enables architects, engineers, contractors, owners, and facility managers to share data throughout the entire lifecycle of the building. The shared data includes the initial design data; geospatial information; financial and legal data; mechanical, electrical, and plumbing layouts; building product specifications, environmental and energy modeling results, and other information. With BIM in place, large amounts of data (typical in moderate and large projects) can be continuously exchanged among the key players. This enables facts, figures, designs and analyses that affect one or more information sources to be constantly updated to ensure that any decisions made on modular building designing are based on accurate information.

8.0  Architectural Designing of Modular Houses

Modular house is the culmination of one type of building system. The building process starts with efficient modern factory assembly line techniques. The prefabricated components are brought to the site and erected using building block type construction. Work is never delayed by curing time or missing materials and can be completed for 30 to 45 working days. Modular buildings and modular homes are sectional prefabricated buildings or houses, which consist of multiple sections called modules. “Modular” is a method of construction differing from other methods .The modules are six sided boxes constructed in a remote facility, then delivered to their intended site of use. Using a crane, the modules are set onto the building’s foundation and joined together to make a single building. The modules can be placed side-by-side, end-to-end, or stacked, allowing a wide variety of configurations and styles in the building layout. Modular buildings, also called prefabricated buildings, differ from mobile homes, which are also called manufactured homes, in two ways. First, modular homes do not have axles or a frame, meaning that they are typically transported to their site by means of flat-bed trucks. Secondly, Modular buildings must conform to all local building codes for their proposed use, while mobile homes, made in the United States, are required to conform to federal codes governed by HUD. There are some residential modular buildings that are built on a steel frame (referred to as on-frame modular) that do meet local building codes and are considered Modular homes, rather than Mobile homes.

Modular Houses are also referred to as Transportable homes, portable homes, pre-manufactured homes, manufactured homes, pre-built homes, granny flats, prefabricated homes, prefabs, prefab homes, cabins, holiday park cabins, tourist cabins and affordable housing. These are all types of modular homes. However, they are not to be confused with a traditionally built house on a block of land that is moved after a period of years and transported to another location. These are purely houses that have been moved. Modular homes shown in Figure 16 (or any other terminology used in the list above) are designed to be transported and have extra reinforcing to cope with possibly several moves over their lifetime (Leu and Hwang, 2002).

8.1. Module House Classification

8.1.1. One Block Prefabricated House

The main characteristics of this type are full prefabrication (Li et al, 2008). The one block prefabricated house is produced not on site; it is fully pre-made with all furniture and technical installations. The main idea of this modular type is to deliver it on site in one peace and with just few modifications, house is ready for inhabitants. A type like this saves time on construction and it is portable with one time travel, it is also saving costs on building site arrangement. Usually time to fully finish mounting modular house is 2-3 month; this time is a lot shorter comparing to standard construction time that could last up to 1 year (Li et al, 2008). Construction worker team instead of constant driving around building sites can produce modular homes at factory that way saving their time and money for producing company and client. If comparing expenses for classical construction and prefabricated house, there is about 30% difference in material costs. Prefabricated house building can reduce expenses of materials ordering them directly from producing companies, avoiding premiums of construction designers. Also the materials are kept under roof without any weather damage. There are also several types of construction for this kind of modular house.

The most common construction is wooden frame shown in Figure 17, insulated in between and decorated with Wooden cladding (Li et al, 2008; Martinez et al, 2008). This type gives less weight which is good for transportation, wooden construction is also cheaper. For this type of construction there are unlimited choice of shape and design, as long as it stays within allowed dimensions for transportation.

One block houses are also made with steel frame, the cladding and insulation can be the same as for wooden frame construction shown in Figure 18. This type of construction gives more weight, but it is easy to mount, this type increases the stability of house and it is also very variable on shapes and design (Mullens, 2004). This type allows using more glass on construction because of strength of frame.

Also depending on location and weather conditions there are possible variations of construction. If the weather is rough and windy than the precast concrete is used for the ground partition. This concrete slab requires for stronger foundation. The modular house later is connected to concrete slab which is used as floor as shown in Figure 19 (Mullens, 2004; Murray et al, 2003)

Another type of construction is oceans container system. Basic container is adjusted to planning of ground floor shown in Figure 20, the windows and doors are cut out in necessary places (Nasereddin et al, 2007). Walls and floors are insulated. This type of construction is very limited for shape variances; it is triangular shape with flat roof.

8.1.2. Multiple Blocks of Prefabricated House

This type of modular housing remains the same principle as one block prefabricated houses shown in Figure 21. The difference is in layout of blocks. There can be more than one block connected together, that way ensuring more space for open planning. One block can be one room, the wet rooms can be made separately in other block (Nasereddin et al, 2007; Navon and Berkovich, 2005).

As shown in Figure 22, the system allows building blocks one to another that way making multi-storey prefabricated house. Managing blocks of this kind can reach unlimited design variances, it can fit any environment and the time process of building is shortened due to prefabrication (Navon and Berkovich, 2005). The blocks are delivered with several trucks and with crane they are connected together. All technical installations are set up beforehand. The stability of those blocks are ensured, each item is made according to load bearing regulations. When connected, blocks obey their own static rules. If blocks are arranged with overhangs, the extra reinforcement is made. Usually the layout of blocks is designed before in factory, therefore all necessary construction reinforcement is provided. The construction of blocks usually is made of steel frame, but there are also wooden constructions and container systems. Once the modules of a portable home are assembled, there is a double wall effect. Where the modules meet, as each module is a mini building in its own way, when connected together, the internal walls are effectively doubled. This type is gaining popularity among motel business, the construction time is short, costs are lower than traditional building and the design does not play important role.

8.1.3. Modular House Assembled on Site

This type of module house is a prefabricated home built in an offsite factory, which is then delivered by truck to the home site, and assembled by a construction crew (Pastor et al, 2001). The sort of this kind home can share some similarities to prefabricated block houses. The materials and way its built could be very similar. The difference between this type and prefabricated block house is that there are more varieties of shape, the size could grow bigger and the main issue is mounting.. This type of construction may be subject to weather conditions – at the moment of mounting. Also the time spent on site assembling this house lasts longer than one block house finishing. As shown in Figure 23, the module house assembled on site doesn’t need to be specially reinforced for transporting.

As long as it is delivered to site in pieces shown in Figure 24, the elements do not suffer from different statistical forces that may influence block house (Navon and Berkovich, 2005). To assemble such a house the crane is required. Building elements are connected piece by piece by construction workers.

All connection holes are later insulated and prevented from thermal bridges. This type of mounting must obey all building regulations. As shown in Figure 25 and 26, the building site is arranged by standards because there are several processes taking place on site and most of those processes concerns work safety (Pastor et al, 2001).

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